Water-soluble coating composition

ABSTRACT

There is disclosed a water-soluble coating composition having excellent properties including corrosion resistance, adhesion, impact resistance and so on. The coating composition comprises an adduct of a butadiene lower polymer or copolymer and α,β-ethylenically unsaturated dicarboxylic acid compound resulting from the special addition reaction, a hydrophilic solvent and a neutralizer.

This is a division of application Ser. No. 518,824, filed Oct. 29, 1974,now abandoned; replaced by Continuation Application Ser. No. 851,905,filed Nov. 16, 1977, now allowed as U.S. Pat. No. 4,145,501.

BACKGROUND OF THE INVENTION

This invention relates to a water-soluble coating composition havingexcellent physical properties including corrosion resistance, adhesion,impact resistance and so on.

Heretofore, as raw materials for a water-soluble coating compositionthere have been used natural oils. However, recently, use of naturaloils for the above purposes has been regarded to be disadvantageousbecause their supply is precarious and they cause pollution in respectof smell and smoke. Therefore, instead of natural oils a butadiene lowpolymer has been given much consideration as a film forming material fora water-soluble coating composition since the coating film formed from abutadiene low polymer or copolymer has very excellent film properties inrespect of chemical resistance, solvent resistance, water resistance,corrosion resistance, levelling property and so forth as compared withthose prepared from the conventional film forming materials such asnatural oils.

In order to prepare a film forming material for a water-soluble coatingcomposition, it is necessary to introduce hydrophilic groups such ascarboxyl, hydroxyl, ether, amino and sulfonic acid groups into themolecular structure of the material.

With regard to the introduction of the carboxyl group in to thebutadiene lower polymer or copolymer, it is well known that an adductcan be prepared by heating it with α,β-ethylenically unsaturateddicarboxylic acid compound. The addition reaction between butadienelower polymer or copolymer and α,β-ethylenically unsaturateddicarboxylic acid is carried out through a radical or thermal reaction.Both reactions are accompanied by cross linking reactions amongmolecules of starting polymer so that gelation of the adduct occurs,which is disadvantageous.

In order to eliminate the above noted difficulties there are known manymethods for preparing such an adduct by the addition of certaincompounds such as hydroquinone, 2, 6-di-tert-butyl-4-methyl phenol,urethane compounds or metallic salts to the thermal reaction system.According to these methods the amount of addition of α,β-ethylenicallyunsaturated dicarboxylic acid compounds is very small, the adduct isgreatly colored, the viscosity of the adduct is too high to be treatedand the molecular weight of the usable starting polymer is limited to avery low range so that the adduct produced by the above conventionalmethods has insufficient properties as a film forming material for awatersoluble coating composition.

With these difficulties in view, the present inventors made extensivestudies on methods for preventing various undesirable side reactionssuch as the above noted gelation from the addition reaction between abutadiene lower polymer or copolymer and α,β-ethylenically unsaturatedcarboxylic acid and as the result found that some compounds haveexcellent effects for the above noted purposes. Japanese patentapplications for the above inventions were filed (Japanese patentapplication Nos. 47-126461 and 48-57676). According to these inventionsaccomplished by the present inventors the undesirable side reactionincluding the gelation of the addition reaction can be completelyprevented without causing any ill effects to the reaction and further anadduct with a large amount of addition can be obtained from startingpolymer having a high molecular weight.

It is an object of the present invention to provide a water-solublecoating composition which will eliminate or alleviate the foregoingdisadvantages encountered with the prior-art coating compositions.

It is a further object of this invention to provide a water-solublecoating composition having excellent properties in respect of corrosionresistance, adhesion, impact resistance and so on.

These objects and other features of this invention will be apparent fromthe following description taken in connection with certain embodimentsof the invention.

BRIEF SUMMARY OF THE INVENTION

As a result of extensive research of the application of the above notedadducts to a water-soluble coating composition, it has found that theabove-mentioned objects of the invention may be achieved by the use ofthese adducts.

Briefly stated, the invention concept of this invention resides in awater-soluble coating composition comprising an adduct (1) of abutadiene lower polymer or lower copolymer (A) and α,β-ethylenicallyunsaturated dicarboxylic acid compound (B) prepared by the reactionbetween said (A) and (B) in the presence of one or more compounds (C)selected from p-phenylene-diamine derivatives, catechol derivatives,pyrogallol derivatives, nitrosamines, quinoline derivatives and naphtolderivatives; a hydrophilic solvent (2); and a neutralizer (3).

DETAILED DESCRIPTION OF THE INVENTION

The butadiene lower polymers used in the present invention are butadienepolymers containing a large proportion of 1,2-double bonds or a largeproportion of 1,4-double bonds or large proportions of both 1,2- and1,4-double bonds. The butadiene polymers which are prepared bypolymerizing butadiene alone or with other monomers in the presence ofalkali metal or organic alkali metal compound as a catalyst, are typicalones used in the present invention. In order to regulate the molecularweight, to reduce the gel content and to form a light-colored polymer,the living polymerization is typically a polymerization which is carriedout in a tetrahydrofuran medium or a chain transfer polymerization inwhich ethers such as dioxane and alcohols such as isopropyl alcohol areadded and aromatic hydrocarbons such as toluene and xylene are used asthe chain transfer agent or the solvent. A lower polymer in which mostof the double bonds the in butadiene units are 1,2-double bonds can beprepared by the above methods, and this lower polymer can be used in thepresent invention. A butadiene lower polymer in which most of the doublebonds in the butadiene units are 1,4-double bonds and which can be usedin the present invention can be prepared by polymerizing butadiene aloneor with other monomers in the presence of a catalyst comprising acompound of a metal of group VIII of the periodic table and in alkylaluminum.

A lower copolymer as referred to in the present invention meanscopolymers of butadiene with conjugated diolefins other than butadienesuch as isoprene, 2,3-dimethyl butadiene and piperylene or withvinyl-substituted aromatic compounds such as α-methyl styrene,vinyltoluene and divinylbenzene as the co-monomers. Butadiene lowercopolymers containing less than 50 percent by weight of said co-monomersmay be preferably used.

Further, in the present invention, modified products of the butadienelower polymer or copolymer which are prepared by heating and partiallyoxidizing the butadiene lower polymer or copolymer with blowing off airin the presence of carboxylic acid metallic salts such as cobaltnaphthenate or manganese octenoate, or prepared by thermal treatment ofthe butadiene lower polymer or copolymer in the presence of an organicperoxide, may also be used.

The butadiene lower polymer or copolymer in the present invention isliquid or semi-solid at room temperature, and the number averagemolecular weight thereof is in the range of 200 to 10,000.

Said α,β-ethylenically unsaturated dicarboxylic acid compounds in thepresent invention may be represented by the following general formula:##STR1## in which X and Y are hydrogen atoms or alkyl groups, and may bethe same or different; and A and B are hydroxyl groups, alkoxyl groupsor an --O-- bond formed by linking A and B together. Saidα,β-ethylenically unsaturated dicarboxylic acid compounds includeanhydrides of maleic acid such as maleic anhydride, citraconic anhydrideand 1,2-diethylmaleic anhydride, and esters of maleic acid such asmonomethylmaleic acid, dimethylmaleic acid and diethylmaleic acid, andthose having 12 or less carbon atoms in each molecule may beadvantageously used.

The amount of α,β-ethylenically unsaturated dicarboxylic acid compoundas used in the present invention is not especially restricted; however,when the adduct is to be used as a water-soluble or water-dispersiblefilm forming material, the rate of addition calculated from the acidvalue and saponification value may not be more than 50 percent byweight, and 3 to 50 percent by weight is preferable. In general, thehigher the rate of addition is, the larger the viscosity becomes. Inaddition to that, the water-solubility of the adduct increases and, as aresult, the water resistance of the water-soluble coating filmdecreases. On the contrary, when the rate of addition is too low, thehydrophilic property of the adduct decreases, and the water-solubilityor water-dispersibility of the adduct is also lowered.

In case an acid anhydride such as maleic anhydride is used as theα,β-ethylenically unsaturated dicarboxylic acid compound of theinvention, the acid anhydride rings are opened after the additionreaction by solvolysis using preferably water or alcohol.

In the addition reaction of a butadiene lower polymer or copolymer, andα,β-ethylenically unsaturated dicarboxylic acid compound of the presentinvention, one or more compounds selected from (1) p-phenylenediaminederivatives, (2) catechol derivatives, (3) pyrogallol derivatives, (4)quinoline derivatives, (5) N-nitrosamines and (6) naphthol derivativesare used.

The above-mentioned p-phenylenediamine derivatives are represented bythe following general formula: ##STR2## in which R₁ and R₂ are the sameor different saturated hydrocarbon groups each having 1 to 20 carbonatoms, or monocyclic and polycyclic aromatic hydrocarbon groups, and R₃is a hydrogen atom or a saturated hydrocarbon group having 1 to 20carbon atoms.

More particularly, the p-phenylenediamine derivatives included in theabove general formula are alkyl-p-phenylene-diamines such asN,N'-dimethyl-p-phenylenediamine, N,N'-diethyl-p-phenylenediamine,N,N'-dipropyl-p-phenylenediamine, N,N'-diisopropyl-p-phenylenediamine,N,N'-di-n-butyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamineand N,N'-di-tert-butyl-p-phenylenediamine; and aromaticgroup-substituted p-phenylenediamines such asN,N'-diphenyl-p-phenylenediamine,N-phenyl-N'-isopropyl-p-phenylenediamine andN,N'-di-β-naphthyl-p-phenylenediamine.

Further, the catechol derivatives in the present invention arerepresented by the following general formula: ##STR3## in which R₁ is asaturated hydrocarbon group or aromatic hydrocarbon group having 1 to 10carbon atoms, and n is an integer which is 0, 1, 2, 3 or 4. As saidcatechol derivatives, there are, for example, alkyl catechols such ascatechol itself, p-methylcatechol, p-ethylcatechol, p-propylcatechol,p-isopropylcatechol, p-n-butylcatechol, p-sec-butylcatechol,p-tert-amylcatechol and 1,2-dihydroxy-3-tert-butyl-5-methylbenzene; andaromatic group-substituted catechols such as p-phenylcatechol andp-(p-methylphenyl) catechol.

Furthermore, the pyrogallol derivatives in the present invention arerepresented by the following general formula: ##STR4## in which R₂ is asaturated hydrocarbon group or aromatic hydrocarbon group having 1 to 10carbon atoms, and m is an integer which is 0, 1, 2 or 3. As saidpyrogallol derivatives, there are, for example, pyrogallol and1,2,3-trihydroxyl-5-methylbenzene.

Furthermore, the N-nitrosamines in the present invention are representedby the following general formula: ##STR5## in which R₁ and R₂ are thesame or different alkyl, cycloalkyl, aryl or naphthyl groups, eachhaving 1 to 20 carbon atoms and each having or not having amino andalkoxy groups as substituent groups. As said N-nitrosamines, there are,for example, N-nitroso-dialkylamines such as N-nitroso-dimethylamine,N-nitroso-diethylamine, N-nitroso-di-n-propylamine,N-nitroso-di-n-butylamine, N-nitroso-di-n-pentylamine andN-nitroso-di-n-hexylamine; N-nitroso-cycloalkylamine such asN-nitrosodicyclohexylamine; and other N-nitrosamines such asN-nitrosodiphenylamine, N-nitroso-dicumenylamine,N-nitroso-ditolylamine, N-nitroso-dixylylamine,N-nitroso-methylphenylamine, N-nitroso-ethylphenylamine andN-nitroso-dinaphthylamine.

Still further, the quinoline derivatives in the present invention arerepresented by the following general formula: ##STR6## in which R₁ is ahydrogen atom or an alkoxy group having 1 to 5 carbon atoms, and R₂, R₃and R₄ are the same or different alkyl groups each having 1 to 5 carbonatoms. As said quinoline derivatives, there are, for example,1,2-dihydro-2,2,4-trimethylquinoline,1,2-dihydro-2,2,4-triethylquinoline,1,2-dihydro-2,2,4-tri-n-propylquinoline,1,2-dihydro-2,2,4-tri-n-butylquinoline,1,2-dihydro-2,2-dimethyl-4-ethylquinoline,1,2-dihydro-2,2,4-trimethyl-6-methoxyquinoline,1,2-dihydro-2,2,4-trimethyl-6-propoxyquinoline and1,2-dihydro-2,2,4-trimethyl-6-n-butoxyquinoline.

Still further, the naphthol derivatives in the present invention arerepresented by the following general formula: ##STR7## in which R₁ andR₂ are hydrogen atoms, alkyl groups each having 1 to 20 carbon atoms,nitro groups, hydroxyl groups or amino groups; n is an integer which is1, 2 or 3; m is an integer of 1, 2, 3 or 4; and one of (R₁)n and (R₂)mis one or more of nitro, hydroxyl or amino groups. As the above naphtholderivatives, there are, for example, dihydroxynaphthalenes such as1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene,1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 1,7-dihydroxy-naphthalene,1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene,2,6-dihydroxynaphthalene and 2,7-dihydroxynaphthalene; amino-naphtholssuch as 1-amino-2-naphthol, 2-amino-1-naphthol, 4-amino-1-naphthol,5-amino-1-naphthol, 6-amino-1-naphthol, 7-amino-1-naphthol,7-amino-2-naphthol, 8-amino-1-naphthol and 8-amino-1-naphthol and8-amino-2-naphthol; and nitro-naphthols such as 1-nitro-2-naphthol.

As disclosed in the above, one or more compounds selected from theabove-mentioned p-phenylenediamine derivatives, catechol derivatives,pyrogallol derivatives, N-nitrosamines, quinoline derivatives andnaphthol derivatives are used as the additive in the preparation of theadduct of α,β-ethylenically unsaturated dicarboxylic acid compound and abutadiene lower polymer or copolymer, in which the amount of saidadditive is in the range of 0.005 to 5 percent by weight, preferably 0.1to 2.0 percent by weight to said butadiene lower polymer or copolymer.When the amount of said additive for inhibiting gelation is too small,the viscosity of the adduct obtained is very much increased, andsometimes, the adduct becomes a gel, or the water-solubilizing of theadduct becomes difficult. On the contrary, it is economicallydisadvantageous to add excess amount of said additive, and such excessaddition sometimes has an adverse effect on the addition reaction. Theeffect of said additive is not decreased even in the presence of otheradditives such as hydroquinone and 2,6-di-tert-butyl-4-methylphenolwhich have little gelation inhibiting effect.

The addition reaction of the present invention between α,β-ethylenicallyunsaturated dicarboxylic acid compound and a butadiene lower polymer orcopolymer in the presence of said additive, may be carried out at atemperature of 120° to 250° C., preferably 150° to 220° C. If thereaction temperature is lower, the reaction period becomes long, and ifthe reaction temperature is too high, there is the risk of gelation eventhough the reaction period may be shortened.

In the present invention, the following oil compound can be added to thereaction system of said butadiene lower polymer or copolymer andα,β-ethylenically unsaturated dicarboxylic acid compound.

Examples of said oil component are (1) animal and vegetable oils havingiodine value of 100 or more such as linseed oil, tung oil, soybean oil,dehydrated castor oil, safflower oil, sardine oil, herring oil and sauryoil; (2) unsaturated fatty acids such as linoleic acid, linolenic acid,oleic acid and α-eleostearic acid; (3) modified oils such as boiled oiland stand oil which are prepared by heat treatment of said animal andvegetable oils listed in the above (1); (4) dimeric acids of the fattyacids as defined in the above (2); and (5) styrenated oil which isprepared by copolymerizing animal or vegetable oil and styrene. Theseoil components may be used with the butadiene lower polymer or copolymerby mixing together in any ratios, and the above mixture can be partiallyoxidized by heating at 60° to 200° C. with blowing off air in thepresence of a conventional drier, namely, a carboxylic acid metal saltsuch as copper naphthenate or manganese octenoate, or said mixture canbe polymerized by heating at a temperature of 50° to 280° C. in thepresence or absence of an organic peroxide such as dicumyl peroxide orbenzoyl peroxide. The thus prepared partially oxidized products andpolymerized products may also be used in the present invention.

In the present invention, when the viscosity of a butadiene lowerpolymer or copolymer is high, a diluent may be used so as to reduce theviscosity and to smooth the addition reaction. Such diluent should havea boiling point which is the same as or lower than the addition reactiontemperature, and be inert to the butadiene lower polymer or copolymer,α,β-ethylenically unsaturated dicarboxylic acid compound,p-phenylenediamine derivatives, catechol derivatives, pyrogallolderivatives, N-nitrosamines, quinoline derivatives and naphtholderivatives. For example, petroleum fractions such as toluene, xyleneand kerosene may be preferably used as the above-mentioned diluents.

The inert gas for the displacement of the reaction system may beselected from among those which are inert to the butadiene lowerpolymer, α,β-ethylenically unsaturated dicarboxylic acid compound andsaid additives; for example, argon, nitrogen and carbon dioxide may bepreferably used.

The adducts of the present invention which are prepared fromα,β-ethylenically unsaturated dicarboxylic acid compound and a butadienelower polymer or copolymer in the presence of p-phenylenediaminederivatives, catechol derivatives, pyrogallol derivatives,N-nitrosamines, quinoline derivatives or naphthol derivatives, arealmost colorless or light brown liquids or semisolids at roomtemperature, and each has a number average molecular weight of 200 to10,000. Through the process of the present invention, the molecularweight of the butadiene lower polymer or copolymer is increased by theaddition of the α,β-ethylenically unsaturated dicarboxylic acidcompound, and the viscosity thereof is somewhat increased, while theiodine value is decreased to some extent.

The adduct of the present invention may be used as a water-solublecoating composition by the addition of a neutralizer in the presence ofa hydrophilic agent or by the addition of the latter after the additionof the former. The coating composition according to the presentinvention, if necessary, may be dissolved or dispersed uniformly by theaddition of a siccative, a pigment and other agents and after that maybe diluted with water according to its purpose. The term "awater-soluble coating composition" used herein means a coatingcomposition which is perfectly dissolved in water or a hydrophilicsolvent, or particles of which are dispersed therein.

A water-soluble coating composition according to this inventiontypically includes so called water paints, electro deposition paint orthe like which are diluted with water when coating.

Hydrophilic agents used herein are hydrogen containing compounds havingsubstantial affinity with water and include alcohols such as methanol,ethanol, butanol and the like; cellosolves such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycolmonobutyl ether and the like; cyclic ethers such as tetra-hydrofuran,dioxane and the like; ketoalcohols such as diacetone alcohol and thelike; ketones such as acetone, methyl ethyl ketone and the like; esterssuch as methyl acetate and the like. The hydrophilic agent may be addedin an amount of less than 100 parts by weight, preferably 5-50 parts byweight, to 100 parts by weight of the butadiene lower polymer orcopolymer. Amounts exceeding 100 parts by weight of this agent areexpensive and impair the quality of the composition as a water solublecoating composition.

Neutralizers used herein are basic compounds and include alkalimetalhydroxides such as sodium hydroxide, potassium hydroxide and the like;aqueous ammonia; organic amines such as alkylamines, includingdiethylamine, triethylamine, N-morpholine, polyamines, includingethylenediamine, diethylenetriamine and the like, alkanolamines such asmonoethanolamine, diethanolamine, triethanolamine and the like,alicyclicamines such as cyclohexylamine and the like. These neutralizersmay be used alone or in combinations thereof and in a range of 0.2 to2.0 equivalents to the amount of α,β-ethylenically unsaturateddicarboxylic acid. Usually these may be used at a pH of 6.0 to 9.0. Morethan 2.0 equivalents of these neutralizers would be expensive and failto leave the coatings with sufficient water resistance.

The siccatives employable in the present invention are those widely usedto accelerate the drying and hardening of an adduct of a butadienepolymer or copolymer and an oil component and α,β-ethylenicallyunsaturated dicarboxylic acid. As the above siccatives, there aremetallic salts of carboxylic acids such as cobalt, manganese, lead,iron, zinc, zirconium and calcium salts of octenic acid, naphthenicacid, rosilic acid and fatty acids of toll oil. The siccatives may beused in an amount of less than 1.0 percent by weight equivalent tometallic part thereof to the adduct. These siccatives are preferablyhighly water dispersible and hydrophilic and are stable in aqueousphase.

The pigments employable in the present invention include inorganicpigments such as titan white, zinc white, lead white, chromium oxide,ultramarine, rouge, carbon black and the like; organic pigments such asnitroso-, nitro-, azo-, lake- and phthalocyanine-type pigments and thelike. These pigments are preferably highly water dispersible andhydrophilic and are stable in aqueous phase.

The water-soluble coating composition according to the present inventionserves as an electrodeposition paint or an immersion deposition paintand forms a tough film by being heated at 100° C. to 250° C. for 2 to 90minutes.

The water-soluble coating composition according to the present inventionis excellent in stability in water and the film of said coatingcomposition coated on both a non-treated steel plate and a chemicallytreated steel plate is excellent with respect to corrosion resistance,throwing power, impact resistance, adhesion, leveling property andhardness.

The following examples are provided to further illustrate the presentinvention, but these are not to be regarded as limiting.

INVENTIVE EXAMPLE I

1,000 parts by weight of a butadiene lower polymer or copolymer having anumber average molecular weight of 1,000 and a viscosity of 42 poise(25° C.), 333 parts by weight of xylene, 163 parts by weight of maleicanhydride and 2 parts by weight ofN-phenyl-N'-isopropyl-p-phenylenediamine were fed into a 2 literstainless steel autoclave provided with a magnetic stirrer. The air inthe reaction system was sufficiently displaced by dried nitrogen gas.The reaction mixture was stirred at 190° C. for 8 hours to cause theaddition reaction between said polybutadiene and maleic anhydride. Afterthe reaction, the autoclave was cooled to room temperature. Then it wastreated in a reduced pressure of 1 mmHg at 150° C. to distill off thesolvent of xylene and a small amount, namely, remaining maleicanhydride, whereby an adduct of maleic anhydride having an acid value of80.0 and a viscosity of 9,500 poise (25° C.) was obtained. 500 parts byweight of the adduct thus obtained were fed to a 1 liter separable flaskhaving a reflux condenser. After the adduct was heated to 70° C., 40parts by weight of water and 10 parts by weight of triethylamine wereadded thereto. The mixture was heated at 80° C. for 2 hours to open therings of the anhydride groups. After 80 parts by weight of ethyleneglycol monoethyl ether was fed to the separable flask, it was cooled toroom temperature. Then the reaction mixture was neutralized with adeionized water solution of triethylamine in such a manner that the pHof the obtained solution will be 8.2 when it contains 10 parts by weightof solids. After that, the solution was diluted with deionized water soas to contain 10 parts by weight of solids. Thus a clearelectrodeposition solution was prepared.

Steel test pieces (0.8 mm×70 mm×150 mm) treated with zinc phosphate wereimmersed in the thus prepared clear electrodeposition solution at 25° C.and electric voltages of 80, 100, 120, 150, 200, 250 and 300 volts,respectively, were applied for 3 minutes under stirring and with 10 cmof a distance between electrodes. The test pieces were thuselectrodeposition coated and taken out from the solution. Then the testpieces were washed with water to remove the superfluouselectrodeposition solution thereon and were air-dried in a room having atemperature of 25° C. and a relative humidity of 75 percent. Afterair-drying, these were put in an oven circulating hot air of 160° C. for30 minutes to harden the films coated thereon. Measurements of thethicknesses of the obtained film showed the following results:(voltage/film thickness) 80 V/10μ, 100 V/12μ, 120 V/13μ, 150 V/15μ, 200V/20μ, 250 V/23μ, 300 V/25μ. All of the films showed excellent filmsurfaces and there were not craters or other defects thereon.

The coated film of 20μ thickness was subjected to various performancetests and exhibited a 4 H pencil hardness, more than 240 hours ofcorrosion resistance, an Erichsen test value of 6.5, a DuPont impacttest value 40 cm and a cross cut test value of 100/100.

COMPARATIVE EXAMPLE I

The procedure described in Inventive Example I was repeated except that3 parts by weight of 2,6-di-tert-butyl-4-methyl-phenol were used as agelation inhibitor in place of 2 parts by weight ofN-phenyl-N'-isopropyl-p-phenylenediamine whereby an adduct of maleicanhydride having an acid value of 76 and a viscosity of 45,000 poise(25° C.) was obtained and then an electrodeposition solution wasprepared in the same manner as in Inventive Example I. Test pieces wereelectrodeposition coated and heated to form film thereon in the samemanner as in Inventive Example I.

The thicknesses of the films varied according to the used voltage asfollows: 80 V/8μ, 100 V/10μ, 120 V/12μ, 150 V/15μ, 200 V/18μ, 250 V/20μ,300 V/21μ.

The whole film surface was not good in gross and leveling property andcraters appeared thereon. The film having a thickness of 20μ wassubjected to various performance tests and showed a pencil hardness of,50 hours of corrosion resistance, an Erichsen test value of 2.0, aDuPont impact test value of 30 cm and a cross cut test value of 65/100.

It is understood from the comparison of Inventive Example I andComparative Example I that various properties of the film produced byusing an adduct of a butadiene lower polymer or copolymer andα,β-ethylenically unsaturated dicarboxylic acid compound as a watersoluble coating composition depend upon the addition of an effectivegelation inhibitor.

Therefore, it is apparent that the adduct according to the presentinvention can be advantageously used as a water-soluble coatingcomposition.

INVENTIVE EXAMPLES II-XII AND COMPARATIVE EXAMPLES II-VII

1000 parts by weight of a butadiene lower polymer or copolymer having anumber average molecular weight of 2,000 and a viscosity of 150 poise(250° C.), 333 parts by weight of xylene, 168 parts by weight of maleicanhydride, 2.0 parts by weight of the gelation inhibitors in InventiveExamples II-XII, 4.0 parts by weight of the gelation inhibitors incomparative Examples II-VI and 10 parts by weight of copper naphthanatein Comparative Example VII were fed into a 2 liter stainless steelautoclave having a magnetic stirrer, respectively. The air in thereaction system was sufficiently displaced by dried nitrogen gas. Thereaction mixture was sufficiently stirred, and heating was continued for8 hours at 190° C. to cause the addition reaction between said butadienelower polymer or copolymer and maleic anhydride. The adduct was preparedin the same manner as in Inventive Example I. To 500 parts by weight ofthe adduct were added 150 parts by weight of water and 20 parts byweight of triethylamine and these were admixed for 30 minutes at 30° C.This admixture was dissolved in 100 parts by weight of ethylene glycolmonobutyl ether. The pH of the adduct solution was adjusted withtriethylamine to 8.3. Thus a water dispersed varnish containing 60percent by weight of a resinous content was obtained. This varnish wascombined with the other additives according to the recipe shown in TableI and dispersed in a ballmill. The resultant sample was diluted withdeionized water to make an electrodeposition solution containing 10percent solids. Steel test pieces were electrodeposition coated withsaid solution in the same manner as described in Inventive Example I.The film coated on the test piece was hardened in a hot air circulationtype oven for 30 minutes at 170° C. The finished test pieces weresubjected to various performance tests, with the results shown in TableII.

                  TABLE I                                                         ______________________________________                                        about 60 percent varnish                                                                           100 parts by weight                                                           (solid content)                                          rutile type titan white                                                                            30 parts by weight                                                            (solid content)                                          carbon black         0.5 parts by weight                                                           (solid content)                                          strontium chromate   1.0 parts by weight                                                           (solid content)                                          ______________________________________                                    

INVENTIVE EXAMPLE XIII AND COMPARATIVE EXAMPLE VII

500 parts by weight of a butadiene lower polymer or copolymer having anumber average molecular weight of 3,500 and a viscosity of 1100 poise(25° C.), 500 parts by weight of linseed oil and 333 parts by weight ofxylene were fed into a 2 liter stainless steel autoclave having amagnetic stirrer. The air in the reaction system was sufficientlydisplaced by dried nitrogen gas. The reaction mixture was stirred andheated at 260° C. for 3 hours and thereafter was cooled to roomtemperature. Then 192 parts by weight of maleic anhydride and 2 parts byweight of N-phenyl-N'-isopropyl-p-phenylenediamine were fed to theautoclave and the air in the reaction system was again displaced bydried nitrogen gas. The reaction mixture was stirred and heated at 190°C. for 10 hours to cause the addition reaction. The adduct was recoveredin the same manner as described in Inventive Example I. The adductshowed an acid value of 90 and a viscosity of 6000 poise (25° C.).

An electrodeposition coating solution containing the above adduct wasprepared in the manner described in Inventive Example II. A test piecewas coated with the coating solution and heated to harden the coatedfilm. The finished test piece was subjected to various performancetests, with the results shown in Table II.

For comparison, the procedure described above was repeated except that 3parts by weight of p-tert-butyl-hydroquinone were used in place of 2parts by weight of N-phenyl-N'-isopropyl-p-phenylenediamine, whereby anadduct having an acid value of 89 and a viscosity of 35,000 poise (25°C.) was obtained and then an electrodeposition solution was prepared inthe same manner as above. A test piece was coated with the coatingsolution and heated to harden the coated film. The finished tests piecewas subjected to various performance test, with the results shown inTable II.

                                      TABLE II                                    __________________________________________________________________________                                                  Characteristics of                       Gelation inhibitor          Adduct   Electrodeposition                                                        Viscosity Film                                                            Acid                                                                              (poise                                                                             Voltage                                                                            thickness                                                                          Throwing                       Structural formula     Amount*                                                                            value                                                                             25° C.)                                                                     (V)  (μ)                                                                             power                 __________________________________________________________________________                                                            (cm)**                 Inventive Example II                                                                   ##STR8##              0.2  80.0                                                                              25,000                                                                             180.sup.V                                                                          24.sup.μ                                                                        20.3                  Inventive Example III                                                                   ##STR9##              "    79.5                                                                              24,000                                                                             180  23   18.4                  Inventive Example IV                                                                    ##STR10##             "    30.0                                                                              23,000                                                                             180  23   19.2                  Inventive Example V                                                                     ##STR11##             "    80.5                                                                              35,000                                                                             180  24   21.1                  Inventive Example VI                                                                    ##STR12##             "    78.5                                                                              30,000                                                                             180  21   19.0                  Inventive Example VII                                                                   ##STR13##             "    79.0                                                                              27,000                                                                             180  23   17.5                  Inventive Example VIII                                                                  ##STR14##             "    79.0                                                                              29,000                                                                             180  19   18.6                  Inventive Example IX                                                                    ##STR15##             "    79.5                                                                              34,000                                                                             180  23   17.4                  Inventive Example X                                                                     ##STR16##             "    80.0                                                                              33,000                                                                             180  24   17.7                  Inventive Example XI                                                                    ##STR17##             "    80.5                                                                              29,000                                                                             180  19   17.2                  Inventive Example XII                                                                   ##STR18##             "    79  31,000                                                                             180  20   16.5                  Inventive Example XIII                                                                  ##STR19##             0.4  90   6,000                                                                             150  23   19.6                  Comparative Example II                                                                  ##STR20##             0.2  gelled during the addition                                                             --action                                                                           --   --                    Comparative Example III                                                                 ##STR21##             0.4  77  45,000                                                                             170  19   11.2                  Comparative Example IV                                                                  ##STR22##             "    76  44,000                                                                             170  21   10.5                  Comparative Example V                                                                   ##STR23##             "    75  50,000                                                                             160  22   10.2                  Comparative Example VI                                                                  ##STR24##             "    77  34,000                                                                             180  20   10.0                  Comparative                                                                            Copper naphtenate      1.0  76  31,000                                                                             180  21    9.0                  Example VII                                                                   Comparative Example VIII                                                                ##STR25##             0.6  89  35,000                                                                             150  21   12.1                           Properties of coated film***                                                                        Dupont Corrosion                                                 adhesion     Impact test                                                                          resistance                                                (cross cut                                                                           Erichsen                                                                            (1/2 inch.,                                                                          (salt spraying                                                                           Solvent                                                                              Pencil                         Film surface                                                                           test)  test  1000g) test)****  resistance                                                                           hardness              __________________________________________________________________________    Inventive                                                                              Lustered and                                                                           100/100                                                                              More than                                                                           50     No change  Excellent                                                                            4H                    Example II                                                                             excellent       7.0          1.5 mm                                  Inventive                                                                              "        100/100                                                                              5.5   50     No change  "      3H                    Example III                           1.5 mm                                  Inventive                                                                              "        100/100                                                                              5.2   50     No change  "      3H                    Example IV                            2.0 mm                                  Inventive                                                                              "        100/100                                                                              6.5   50     No change  "      4H                    Example V                             1.5 mm                                  Inventive                                                                              "        100/100                                                                              5.3   50     No change  "      2H                    Example VI                            3.0 mm                                  Inventive                                                                              "        100/100                                                                              6.2   50     No change  "      3H                    Example VII                           2.5 mm                                  Inventive                                                                              "        99/100 5.1   50     No change  "      4H                    Example VIII                          3.0 mm                                  Inventive                                                                              "        100/100                                                                              5.0   40     No change  "      4H                    Example IX                            3.0 mm                                  Inventive                                                                              "        99/100 6.0   50     No change  "      3H                    Example X                             2.5 mm                                  Inventive                                                                              "        96/100 5.1   40     No change  "      3H                    Example XI                            3.0 mm                                  Inventive                                                                              "        99/100 5.3   40     No change  "      2H                    Example XII                           2.5 mm                                  Inventive                                                                              "        100/100                                                                              6.5   50     No change  "      3H                    Example XIII                          1.5 mm                                  Comparative                                                                            --       --     --    --     --         --     --                    Example II                                                                    Comprative                                                                             Lusterless                                                                             65/100 2.1   30     rusted on the                                                                            poor   F                     Example III                                                                            coarse and                   whole surface                                    craters                      9 mm                                             appeared                                                             Comparative                                                                            "        75/100 2.0   30     rusted on the                                                                            "      F                     Example IV                            whole surface                                                                 8 mm                                    Comparative                                                                            "        85/100 2.5   30     rusted on the                                                                            Bad    B                     Example V                             whole surface                                                                 10 mm                                   Comparative                                                                            "        70/100 2.0   30     rusted on the                                                                            "      B                     Example VI                            whole surface                                                                 10 mm                                   Comparative                                                                            Lustrous and                                                                           85/100 3.2   30     rusted on the                                                                            "      less than             Example VII                                                                            sticky                       whole surface     2B                                                          15 mm                                   Comparative                                                                            coarse and                                                                             90/100 3.2   40     rusted on the                                                                            poor   F                     Example VIII                                                                           craters                      whole surface                                    appeared                     7.5 mm                                  __________________________________________________________________________     NOTE:-                                                                        *Amounts of gelation inhibitors are parts by weight per 100 parts by          weight or a butadiene lower polymer.                                          **Throwing power: These values were measured by the use of a usual            throwing power measuring device (pipe method) and show amounts                electrodeposited on a measuring plate in a pipe (a length of the              electrodeposited plate part) when applying a necessary voltage for 3          minutes so as to cause a film deposited on an outer standard plate to be      20 - 25μ. Higher values appearing in the Table show superiority in         throwing power.                                                               ***Coated film performance tests were conducted according to JIS K 5400.      ****Corrosion resistance:The coated film on the test piece was cut with a     knife to make two crossed cut lines reaching to the test piece surface.       The thus cut test piece was subjected to a salt spraying test for 400         hours according to JIS Z2371 and then washed with clean water and             air-dried. Directly after that, two cellophane tapes were put on the two      crossed cut lines, respectively, and then stripped off. These values were     given by the largest length of the rusted surface from the line.         

What is claimed is:
 1. A water-soluble coating composition comprising anadduct ( 1) of a butadiene lower polymer or lower copolymer (A) whichhas a number average molecular weight in a range of 200-10,000 and isliquid or semi-solid at room temperature and α,β-ethylenicallyunsaturated dicarboxylic acid compound (B) resulting from the reactionof said (A) and (B) at a temperature in the range of 120° to 250° C. inthe presence of at least one N-nitrosamine derivative (C) in an amountof 0.005 to 5 percent by weight of said (A); a hydrophilic solvent (2)in an amount of less than 100 parts by weight to 100 parts by weight ofsaid (A); and a neutralizer (3) in a range of 0.2 to 2.0 equivalents tosaid (A).
 2. The water soluble coating composition as claimed in claim1, in which said N-nitrosamines derivative (c) isN-nitroso-dimethylamine, N-nitroso-diethylamine,N-nitroso-di-n-propylamine, N-nitroso-di-n-butylamine,N-nitroso-di-n-pentylamine, N-nitroso-di-n-hexylamine,N-nitroso-dicyclohexylamine, N-nitroso-diphenylamine,N-nitroso-dicumenylamine, N-nitroso-ditolylamine,N-nitroso-dixylylamine, N-nitroso-methylphenylamine,N-nitroso-ethylphenylamine or N-nitroso-dinaphtylamine.
 3. The watersoluble coating composition as claimed in claim 1, in which saidα,β-ethylenically unsaturated dicarboxylic acid compound (B) is maleicanhydride, citraconic anhydride, 1,2-diethylmaleic anhydride, maleicacid monomethyl ester, maleic acid dimethyl ester or maleic acid diethylester.
 4. The water soluble coating composition as claimed in claim 1,in which said amount of (C) is 0.1 to 2.0 percent by weight to said (A).5. The water soluble coating composition as claimed in claim 1, in whichthe reaction mixture of said addition reaction is heated to 150° to 220°C.
 6. The water-soluble coating composition as claimed in claim 1, inwhich said hydrophilic solvent (2) is methanol, ethanol, buthanol,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, tetrahydrofuran, dioxane, diacetonealcohol, acetone, methyl ethyl ketone or methyl acetate.
 7. Thewater-soluble coating composition as claimed in claim 1, in which saidneutralizer (3) is sodium hydroxide, potassium hydroxide, ammonia water,diethylamine, triethylamine, N-morpholine, ethylenediamine,diethylenetriamine, monoethanolamine, diethanolamine, triethanolamine orcyclohexylamine.
 8. The water-soluble coating composition as claimed inclaim 1, which further comprises siccatives.
 9. The water-solublecoating composition as claimed in claim 1 which further comprisespigments.
 10. The water-soluble coating composition as claimed in claim2, in which said (C) consists of one or more of said N-nitrosaminesderivatives.
 11. A water-soluble coating composition comprising anadduct (1) of a butadiene lower polymer or lower copolymer with aco-monomer (A) selected from the group consisting of isoprene,2,3-dimethyl butadiene, piperylene, α-methyl styrene, vinyltoluene anddivinylbenzene, said polymer or copolymer having a number averagemolecular weight in the range of 200-10,000 and being liquid orsemi-solid at room temperature and α,β-ethylenically unsaturateddicarboxylic acid compound (B) selected from the group consisting ofmaleic anhydride, citraconic anhydride, 1,2-diethylmaleic anhydride,maleic acid monomethyl ester, maleic acid dimethyl ester and maleic aciddiethyl ester resulting from the reaction of said (A) and (B) at atemperature in the range of 120° to 250° C. in the presence of at leastone N-nitrosamine derivative (C) in an amount of 0.005 to 5 percent byweight of said A; a hydrophilic solvent (2) in an amount of less than100 parts by weight to 100 parts by weight of said (A), said hydrophilicsolvent (2) being selected from the group consisting of methanol,ethanol, butanol, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, tetrahydrofuran,dioxane, diacetone alcohol, acetone, methyl ethyl ketone and methylacetate; and a neutralizer (3) in a range of 0.2 to 2.0 equivalents tosaid (A), said neutralizer being selected from the group consisting ofsodium hydroxide, potassium hydroxide, ammonia water, diethylamine,triethylamine, N-morpholine, ethylenediamine, diethylenetriamine,monoethanolamine, diethanolamine, triethanolamine and cyclohexylamine.12. A water-soluble coating composition comprising an adduct (1) of abutadiene lower polymer or lower copolymer with a co-monomer (A)selected from the group consisting of isoprene, 2,3-dimethyl butadiene,piperylene, α-methyl styrene, vinyltoluene and divinylbenzene and 3-50percent by weight of an α,β-ethylenically unsaturated dicarboxylic acidcompound (B) selected from the group consisting of maleic anhydride,cirtaconic anhydride, 1,2-diethylmaleic anhydride, maleic acidmonomethyl ester, maleic acid dimethyl ester and maleic acid diethylester resulting from the reaction of said (A) and (B) at a temperatureof 120°-250° C. in the presence of from 0.005-5 percent by weight to theamount of said (A) of at least one N-nitrosamine derivative (C); ahydrophilic solvent (2) selected from the group consisting of methanol,ethanol, butanol, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, tetrahydrofuran,dioxane, diacetone alcohol, acetone, methyl ethyl ketone and methylacetate in an amount of less than 100 parts by weight to 100 parts byweight of the amount of said (A); and a neutralizer (3) selected fromthe group consisting of sodium hydroxide, potassium hydroxide, ammoniawater, diethylamine, triethylamine, N-morpholine, ethylenediamine,diethylenetriamine, monoethanolamine, diethanolamine, triethanolamineand cyclohexylamine in the amount of 0.2 to 2.0 equivalents to theamount of said (A).